The purpose of these investigations is to identify drugs that will increase tensile strength of arterial and valvular connective tissue in man. Using the domesticated white turkey as an experimentally available test mode system (spontaneous fragmentation of elastic membranes and aneurysms of the abdominal aorta), we find a relationship between the adrenergic input, the chemistry of elastin lysyl-derived cross-links and the tensile strength of the abdominal aorta. This adrenergic input is modified by androgenic steroids. For application of the results from the turkey model onto humans with weaknesses of connective tissue structures, we developed techniques for measuring the desmosines in a 24-hour urine sample. Since desmosines are unique to elastin, a quantification of urinary desmosines provides an index of elastin catabolism in man. Results obtained over the past year show low levels of the desmosines in the urine of patients with Marfan's Syndrome, and these urinary levels are affected by the drugs that alter the lysyl-derived cross-links of the abdominal aorta in the turkey model.